Flat ultrasonic radiators



Nov. 30, 1965 JEAN-CLAUDE SIMON ETAL 3,221,295

FLAT ULTRASONIC RADIATORS Filed May 20, 1963 2 Sheets-Sheet 1 30, 1965 JEAN-CLAUDE SIMON ETAL 3,221,295

FLAT ULTRASONIC RADIATORS Filed May 20, 1963 2 Sheets-Sheet 2 Z I i /2 I I 61 5 I I FIG? United States Patent Ofiice 3,221,295 Patented Nov. 30, 1965 3,221,295 FLAT ULTRASONIC RADIATORS Jean-Claude Simon and Serge Lowenthal, Paris, France, assignors to CSF-Compagnie gnrale de tlgraphie Sans Fil, a corporation of France Filed May 20, 1963, Ser. No. 282,833 Claims priority, application France, May 24, 1962, 898,579, Patent 1,332,016 6 Claims. (Cl. 34.0)

The present invention relates to ultrasonic radiators or antennas, more particularly of the flat type.

Ultrasonic radiators of the type comprising thin plates, which are cause to vibrate in bending, by exciting them by means of electro-acoustical transducers are known in the art.

Some radiators of this type have a structure whose geometry varies periodically in the longitudinal direction. For example, they comprise transversal equidistant strips of a reflecting material, which are applied on the radiating face of the plate.

This arrangement not only makes capable of radiating a structure of dimensions such that the phase velocity of the bending vibration is lower than that of the sound in the ambient medium, but also makes it possible to scan the space by the beam transmitted, by varying the vibration frequency.

Such radiators have a highly directional radiating pattern lengthwise of the plate. However, for technological reasons, the width of the plate should not be large with respect to the wavelength of the transmitted wave. It follows that the transmitted beam is not directive transversally of the plate. In other words, the transmitted beam will have a plane of maximum radiation direction and not only one direction of maximum radiation.

It is an object of the invention to avoid this drawback. The radiator according to the invention has a radiation pattern having only one maximum radiation direction and is capable of performing a scanning in elevation and a scanning in bearing of the ambient medium.

It comprises a plurality of flat radiating elements of the above type which are located in the same plane and side by side, and suitably spaced apart.

A radiator according to the invention has at least some of the following features:

(a) The radiating elements have the same geometrically periodical structure and vibrate in bending.

(b) The exciters which apply thereto a shearing stress, are located in the same transversal plane.

(c) The scanning in elevation is obtained by frequency modulating the exciters.

(d) The scanning in bearing is obtained by phaseshifting each exciter with respect to adjacent ones.

The invention will be best understood from the following description and appended drawings, wherein:

FIG. 1 is a perspective view of a radiator according to the invention;

FIGS. 2 and 3 are respectively a plane and an end view of the radiator of FIG. 1; and

FIGS. 4 and 5 are examples of the application of the invention.

FIGS. 1, 2 and 3 show a radiator comprising four identical radiating elements 1, including thin plates, placed side by side. Their common length is great with respect to their width, which, in turn, is large with respect to their thickness. To each element 1 is secured an exciter 2, which applies a shearing stress thereto.

Electromagnetic exciters 2 which also may be, for ex ample, of the piezoelectric type, comprise matching elements 3, which rest on the respective plates 1. Matching elements 3 are aligned. Elements 1 vibrate in bending and carry similar and uniformly spaced strips 4 of sound reflecting material.

It is known that the individual radiation pattern of such elements is in a plane forming an angle 0 with the plane Oxy of the plate, Ox being the longitudinal direction of plates 1 and 0y being perpendicular to Ox. The magnitude of angle 0 depends on the pitch of the geometrical periodicity of the plates, i.e. on the distance a between two successive strips 4 and on the frequency of the radiated wave. Accordingly, for a given plate 1, andgle 0 may be varied by varying the frequency f of the exciter.

As indicated above, each plate 1 has no directivity in the transverse direction.

However, with a plurality of plates 1, there is a directivity in the transverse direction. If all the plates are excited in phase, the direction of maximum radiation is contained of the plane of symmetry.

However, as is known, if the phase of the exciters progressively increases from one plate to the adjacent one, the direction of maximum radiation will make with the plane of symmetry an angle a which depends on the phaseshift 1// between the adjacent plates and on the distance therebetween.

It follows that, by varying (p, angle or can be also varied. Since angle 0 is the bearing of the radiated beam with respect to the axes Oxyz, associated with the radiator, while a is the angle of elevation, a scanning in bearing and in elevation can thus be readily obtained.

FIG. 4 shows an arrangement for achieving this end.

The electrical circuits which feed the exciters 2 are connected in parallel and fed by means of a variable frequency source 5. A suitable adjusting device 8 includes a plurality of ganged phase-shifters 7, connected between each exciter and the common source 5 in such a way as to provide a variable phaseshift; the first phaseshifter 7 provides a phaseshift (p, the second a phaseshift 2 0, the third a phaseshift 3 0. As a non-limiting example, the device 8 may be of the type described in Electronics Vol. 30, No. 11, McGraW-Hill 1957, page 175, by George E. Pihl.

As to the elevation, it is varied by varying the frequency of source 5.

FIG. 5 shows another application of the invention.

The radiator of FIG. 1 is applied on the hull 9 of a ship, parallel to the longitudinal axis thereof. The device 8 of FIG. 4 is controlled by a gyro 10 which delivers a voltage proportional to the rolling angle G of the ship.

Angle 0c is then controlled by the rolling of the ship. It is thus possible to stabilize in elevation the radiation direction of the radiator, whatever the rolling of the ship.

Of course the invention is not limited to the embodiments described and shown which were given solely by way of example.

What is claimed, is:

1. A radiator for sound waves comprising in combination: a plurality of identical flat and coplanar radiating elements located side by side and equally spaced apart, said elements having the same geometrically periodical structure; means for exciting in each of said elements a bending vibration; a plurality of phaseshifters for feeding said means and means for varying the frequency of said vibration.

2. A radiator for sound waves comprising in combination: a plurality of identical flat and coplanar radiating elements, located in the same plane side by side and equally spaced apart; means for exciting in each of said elements a bending vibration in a predetermined direction; said elements having the same geometrically periodical structure in said direction; a plurality of phaseshifters for feeding said means and means for varying the frequency of said vibration.

3. A radiator for sound waves comprising in combination: a plurality of flat elongated and rectangular elements, located parallel to each other and side by side in the same plane, and equally spaced apart; each of said elements having two ends; means .for exciting a bending vibration propagating from one of said ends towards the other in each of said elements; said elements having a geometrically periodical structure from one end to the other; means for varying synchronously the frequency of said vibrations; and means for phase shifting by the same controllable phaseshift (p, the phase of the vibration in each of said elements with respect to the phase of an adjacent one.

4. A radiator for sound waves comprising in combination: a plurality of flat elongated rectangular elements, located parallel to each other and side by side in the same plane, and equally spaced apart; each of said elements having two ends; vibrator means for exerting on said elements a shearing effect for exerting therein a bending vibration propagating in each of said elements from one end towards the other; said elements having a geometrically periodical structure from one end to the other; means for varying synchronously the frequency of said vibrator means; and means for phase-shifting by the same controllable phaseshift go, the phase of the vibration of each element relating to the phase of an adjacent one.

5. On the hull of a ship, a radiator for sound waves comprising in combination: a plurality of flat elongated rectangular elements, located parallel to each other and side by side, and equally spaced apart; each of said elements having two ends; vibrator means for exerting on said elements a shearing effect for creating therein a bending vibration, propagating in each of said elements from one end towards the other; said elements having a geometrically periodical structure from one end to the other; means for varying synchronously the frequency of said vibrator means; means for phaseshifting by the same controllable phaseshift p, the phase of the vibration of each element relating to the phase of an adjacent one; and means for controlling said phaseshift, said means being controlled by the rolling of the ship.

6. A radiator for sound waves comprising in combination: a plurality of flat elongated rectangular elements, located parallel to each other and side by side in the same plane, and equally spaced apart; each of said elements having two ends; electromagnetic vibrators including acoustic impedance matching means for exerting on;said elements a shearing effect for creating therein a bending vibration propagating in each of said elements References Cited by the Examiner UNITED STATES PATENTS 12/1936 Pierce 340-6 X 1/1948 Mason 340l6 X CHESTER L. JUSTUS, Primary Examiner. 

1. A RADIATOR FOR SOUND WAVES COMPRISING IN COMBINATION: A PLURALITY OF IDENTICAL FLAT AND COPLANAR RADIATING ELEMENTS LOCATED SIDE BY SIDE AND EQUAPPLY SPACED APART, SAID ELEMENTS HAVING THE SAME GEOMETRICALLY PERIODICAL STRUCTURE; MEANS FOR EXCITING IN EACH OF SAID ELEMENTS A BENDING VIBRATION; A PLURALITY OF PHASESHIFTERS FOR FEEDING SAID MEANS AND MEANS FOR VARYING THE FREQUENCY OF SAID VIBRATION. 